The present invention relates to analysis of motion. In particular, medical diagnostic ultrasound data is used to analyze tissue motion.
Intrinsic patient involuntary movements cause motion of tissue and blood in ultrasound images. In the cardiovascular systems, blood, cardiac, vessel or other movements determine abnormal and normal clinical states. Medical diagnostic ultrasound imaging is used to assist in diagnosis. For example, breathing, cardiac pulsations, arterial pulsations and muscle spasms are imaged. The heart rate may be used in conjunction with imaging for visual assessment of cardiac motion. The visual assessment identifies abnormal operation and wall thickening. For muscular skeletal examinations, joint and ligament motions may provide diagnostic information.
Doppler tissue imaging, strain rate imaging, M-mode imaging, examination of a sequence of B-mode images, or detecting the outline or borders of chambers of a heart following myocardial wall motion are used to diagnose cardiac motion. These various modes of ultrasound imaging maybe time-consuming or difficult. For example, tissue Doppler imaging is angle dependent, and strain or strain rate imaging is time-consuming. As another example, boundary detection is sensitive to ultrasound speckle noise. In addition, those methods provide no direct motion timing assessment.
Cardiac resynchrony therapy is used to restore heart function, but may have a limited success, such as 60-70%. The unsuccessful cases are either not improved or worsened. Since cardiac resynchrony therapy is a high cost operation with some risks, it is desirable to prescreen the patients before the operation. The location and timing of a pacemaker is desirably optimized during the operation. Follow-up examination is also desired. Imaging may assist this or other therapies.
Phase and/or amplitude analysis of ultrasound data provide parametric imaging, such as disclosed in U.S. Publication No. 2005/0107704, published May 19, 2005, (U.S. application Ser. No. 10/713,453), the disclosure of which is incorporated herein by reference. A sequence of images is analyzed to determine the onset time of periodical motion as well as the amplitude of the motion. Pixel intensity changes in two-dimensional image sequences are analyzed with the Fournier transform. The relative phase of the first harmonic to the heart cycle identifies the onset time of motion, and the amplitude represents the motion magnitude. A series of images with isolated phase information are then generated. The phase intervals for the isolated phase information shift as a function of time within the cardiac cycle. As a result, the contractions of the heart are visually highlighted in a same way but for different phases throughout the heart cycle. Amplitude analysis may be used to generate images with reduced speckle content or to better detect borders.